1. Field of the Invention
The present invention relates to a toner conveying unit, and more particularly, to a toner conveying unit that collects waste toner discharged from a cleaner for a transfer belt and cleaners for photoreceptor drums of an image forming apparatus and efficiently conveys the waste toner to a toner storage container.
2. Description of the Related Art
In the past, there has been an electrophotographic image forming apparatus. The electrophotographic image forming apparatus includes photoreceptor drums that carry toner images developed into at least electrostatic latent images and a transfer belt that directly or indirectly transfers the toner images carried by the photoreceptor drums to a recording medium.
Since residual toner, which is not transferred to the transfer belt, is generated on the photoreceptor drums, drum cleaners for collecting this residual toner as waste toner are disposed. Further, since residual toner, which is not transferred to the recording medium, is generated even on the transfer belt, a belt cleaner for collecting this residual toner as waste toner is disposed.
The waste toner, which is collected by the drum cleaners or the belt cleaner, is further collected into a waste toner storage container through waste toner conveying passages. The waste toner storage container, which is full of the collected waste toner, is separated and discarded from the image forming apparatus, and a new waste toner storage container is mounted on the image forming apparatus.
Meanwhile, when not only waste toner but also toner is generally conveyed, a conveying passage is divided into a horizontal conveying passage and a vertical conveying passage so that the toner or the waste toner is conveyed to the final destination while being successively conveyed in the horizontal and vertical directions.
For example, even when a developing unit is replenished with toner from a toner cartridge, the conveying passage is divided into the horizontal and vertical directions. Further, toner is forcibly conveyed in the horizontal direction by a screw member, but free fall is often used for the conveyance of toner in the vertical direction.
In general, toner is originally a non-magnetic material, but is electrostatically charged with a predetermined polarity due to the agitation performed by an agitating member, friction generated from blades, or the like for the convenience of development. Accordingly, at a point where the direction of the conveying passage is changed into a vertical direction from a horizontal direction or into a horizontal direction from a vertical direction, a toner pile is apt to be formed by electrostatic adsorption at a portion where a conveying member, an agitating member, or the like is not provided.
In JP-A-2010-078797, a crushing member is disposed at a connecting portion between a vertical passage of a toner cartridge and a vertical passage of a developing unit so as to prevent a toner pile from being formed in the vertical passages. Meanwhile, in the JP-A-2010-078797, the crushing member is disposed close to the toner cartridge, that is, the side from which toner is supplied. A hook portion is formed at an end portion of the crushing member, and the hook portion is rotatably mounted on a crank portion of an agitator that agitates toner and conveys the toner to the vertical passage.
Accordingly, the crushing member expands and contracts with the rotation of the agitator that agitates toner and conveys the toner to the vertical passage. That is, when the crank portion of the agitator is positioned distant from the vertical passage, the crushing member is in an extension state. When the crank portion of the agitator is positioned close to the vertical passage, the crushing member is in a contraction state. The crushing member crushes hardened toner by repeatedly expanding and contracting as described above.
However, an engagement portion is formed at an end portion opposite to the hook portion of the crushing member of JP-A-2010-078797, and the crushing member is fixed to a wall of a supply passage when the engagement portion is engaged with a recess formed on the inner wall of the vertical passage. For this reason, there is a problem in that a toner pile adhering to the inner wall surface of the vertical passage cannot be crushed.
Further, if a form of conveying toner disclosed in JP-A-2010-078797 is applied to a waste toner conveying mechanism, the crushing member is disposed for the drum cleaner of each developing unit that is the side from which waste toner is supplied. For this reason, there is a problem in that the structure of an image forming unit becomes complicated and an increase in cost is caused due to the increase in the number of parts.
Furthermore, like toner that contributes to development and transfer, a bias voltage is applied to waste toner at the time of both development and transfer. That is, waste toner has strong electric charges unlike toner which is replenished from the toner cartridge and to which a bias voltage is not yet applied.
The waste toner, which has strong electric charges as described above, starts to adhere to the inner surface of a lower vertical wall from a receiving port, at which the direction of the waste toner conveying passage is changed into a vertical direction from a horizontal direction, due to an electrostatic force. The amount of the waste toner, which starts to adhere, is gradually increased and the waste toner becomes staying toner. Moreover, deposited waste toner forms a waste toner pile, so that the receiving port is completely clogged.
The waste toner, which is sequentially accumulated from the inner wall of the receiving port to the center of the inner wall as described above, is not conveyed despite the rotation of a conveying screw that is provided on the side from which toner is supplied. Further, the waste toner, which does not have a destination, is accumulated in a waste toner discharge port and the cleaner.
As the waste toner is accumulated, the waste toner overflows to the outside of the cleaner and causes a defective image. Furthermore, the rotation failure of a waste toner discharge/conveying screw is caused by the pressure of the accumulated waste toner. In the end, a disadvantageous state such as unrecoverable breakage is caused.
Since the waste toner has strong electric charges as described above, the waste toner is apt to adhere to the inner wall of the conveying passage in the conveying passage that is used to collect the waste toner and a waste toner pile is apt to be easily formed. It is not possible to prevent the formation of this toner pile through the disposition of the same crushing member as the crushing member that is disposed for the toner replenished from the toner cartridge.
The invention has been made to solve the above-mentioned problems in the related art, and an object of the invention is to provide a waste toner conveying unit that collects waste toner discharged from a cleaner for a transfer belt and cleaners for photoreceptor drums of an image forming apparatus and efficiently conveys the waste toner to a waste toner storage container without forming a waste toner pile in a conveying passage through which the waste toner is conveyed.